1. Field of the invention
The present invention relates generally to the field of treating workpieces with a treating liquid. More specifically, the invention relates to an apparatus for cleaning metallic workpieces prior to a heat-treatment to be performed thereafter.
2. Prior art
U.S. Pat. Nos. 5,268,035 and 5,268,036 disclose methods and apparatuses for cleaning, inter alia, metallic workpieces. The disclosure of these two U.S. patent specifications is herewith incorporated herein by reference.
According to this prior art method and apparatus metallic workpieces are cleaned in a washing vessel. For this purpose, the washing vessel is filled by means of a pressureless splash douche mounted under the washing vessel cover. A pressureless flow of washing liquid emerging from the splash douche flows over the workpieces arranged below the douche. This process is continued until a desired filling level of the liquid is reached in the washing vessel.
During one of the subsequent cleaning steps, the air space left in the washing vessel above the liquid is evacuated until a vacuum below the saturation steam pressure of the liquid is attained. In this way it is possible to cause the liquid to start boiling, and have the workpieces treated by rising steam bubbles at a temperature substantially below 100.degree. C.
According to the prior art apparatus, a certain amount of equipment and instrumentation is required for filling the washing vessel and then performing the various cleaning steps.
It is, therefore, an object underlying the present invention to improve an apparatus of the type specified at the outset such as to permit the filling equipment and instrumentation to be simplified and, hence, reduce costs.